1. Field of Invention
The present invention relates to a self-drilling screw carrying, at least in some regions, a thread, a head provided at one end of the shaft, and a drilling tip provided at another, opposite end of the shaft. The drilling tip has at least one first cutting edge, at least one second cutting edge, a first chip channel associated with the first cutting edge, beginning at a first start point at a free end of the drilling head, and located on a first side of the drilling tip, and a second chip channel associated with the second cutting edge, beginning at a second start point at the free end of the drilling tip, and located on a second side of the drilling tip opposite the first side. The drilling tip has a center located on the longitudinal axis of the screw defined by the shaft.
2. Description of Prior Art
Self-drilling screws of the type described above are used, e.g., for screwing metal sheets to metal beams primarily in roof and wall constructions for screwing trapezoidal and profiled metal sheets to steel girders. The self-drilling screw is provided with a drilling tip that drills a hole through the sheet and girder. Finally, the screw taps a thread and tightens the sheet and girder together.
German Publication DE 198 03 672 A1 discloses a self-drilling screw having a shaft, a head provided at one end of the shaft, and a drilling tip provided at another, opposite end of the shaft and having first cutting edge, and second cutting edge. The drilling tip has two chip channels extending, respectively, from respective cutting edges in the direction of the head along the longitudinal axis of the screw. The chip channels serve for removal material chips produced as a result of drilling. The start points of both chip channels on the respective cutting edges are arranged rotationally symmetrically on the drilling tip. Between the drilling tip and the head, the shaft of the self-drilling screw is provided with a tapping thread.
The drawback of the self-drilling screw of the type described above consists in that the drilled out material of a workpiece is squeezed in the center of the drilling tip, which lies on the longitudinal axis of the screw, and must be removed in a deformed state. This requires application of a high force by the user when pressing the self-drilling screw against a workpiece with a screw-driving tool.
Accordingly, an object of the present invention is to eliminate the above-mentioned drawback of the known self-drilling screw.